Conformal Coating for Automotive Applications
Posted by Sean Horn
Wednesday, September 18, 2013 8:08
@ 8:08 AM
More and more, cars aren’t just made of steel, aluminum, plastic and silicon. Parylene is becoming one of the most useful tools in an automaker’s arsenal. From protecting internal sensors and circuit boards to keeping LED indicator lights bright and color-accurate, Parylene conformal coatings are an important part of protecting today’s sensitive automotive electronics.
Parylene is a unique conformal coating in that it gets applied in a vacuum while in a gaseous state. This allows it to truly cover every surface on a coated item with a complete and pinhole-free coating. At the same time, the coating can be impermeable at anything above 1.4 nanometers (nm), which is more than thin enough to be suitable for areas that require tight tolerances, such as micro-electro-mechanical systems (MEMS).
Unlike some other coatings, Parylene is also extremely tough. It can easily withstand the cold of a car parked outside during a Minnesota winter, the heat of an interior exposed to the Arizona sun in summer, or the temperature of an engine’s combustion chamber. The coating is also so chemically inert that it can withstand exposure to brake fluid, antifreeze, salt air and even automotive chemicals with solvent properties like gasoline.
Modern cars contain approximately 100 million lines of code and have advanced circuitry with scores of microprocessors. Those circuit boards must be rugged, small and extremely reliable. Coating them with Parylene solves two problems. First, it provides protection from the harsh atmosphere inside a car, shielding the electronics from chemical fumes, temperature variations and particulate matter that could damage it or gradually coat its traces, causing thermal issues or short circuits. Second, Parylene is also an excellent dielectric that provides insulation. This allows traces on the PC board to be closer together, shrinking the component size. It also reduces the risk that other nearby electronics will interfere with the coated board’s operation.
Modern cars are filled with microelectronics and sensors that measure performance and allow the vehicle to retune itself for better efficiency or power delivery. These sensors can be exposed to extremely harsh conditions. Fuel lines driven by high-pressure pumps contain flow sensors, while engine components have temperature sensors. Tire pressure sensors and inertial sensors are exposed to dust and vibration, while manifold pressure sensors have to withstand searing temperatures. Parylene protects these small parts from damage. It can also be masked to leave sensor surfaces that need to be exposed uncoated.
The gaskets, seals and hoses throughout cars also benefit from Parylene coating. As with other parts, Parylene protects them from both the harsh conditions inside the car, as well as the chemical properties of the fluids or compounds that they carry or hold in place.
Parylene is also an excellent lubricant. This helps those compounds flow past the seal without turbulence. It also can make coated components easier to install or to remove for service.
Light emitting diodes (LEDs) offer long life, excellent illumination and low power consumption—all important characteristics for automotive applications. Unfortunately, they’re also very sensitive to ultraviolet (UV) light, which is a major drawback. While some Parylene formulations are also UV-sensitive, UV-stable coatings are also available.
UV-stable coatings don’t just withstand damage themselves. They also protect the coated LEDs from being damaged by UV radiation. Specially formulated Parylene from Diamond-MT offers UV protection at a lower cost than other Parylene applications.